The present invention relates to a gas turbine engine component comprising at least one ring element and a plurality of circumferentially spaced arms extending in a radial direction of the ring element.
The invention also relates to a turbojet engine provided with such a gas turbine engine component, as well as an aircraft provided with such a turbojet engine.
In particular, the invention relates to a component that defines a part of a fan and wherein there are provided aerodynamic guide vanes for the guiding of gases in a by pass channel of the engine and wherein there are also provided structural vanes or load carrying vanes designed to secure the load-carrying ability of the fan assembly, and wherein said arms define either of said types of vanes. However, in a broad sense, the invention relates to all kinds of structures in turbojet engines wherein there is a plurality of arms, typically vanes or load carrying vanes, connected to an outer ring element. For example, such structural vanes may be arranged in an engine core gas channel, but also in a fan section of an engine type where the fan section is arranged in a common gas channel upstream of a division into a core gas channel and a bypass gas channel.
Furthermore, the invention is particularly advantageous, and therefore includes, components of turbojet engines by which the above-mentioned arms and the ring element comprises an anisotropic material such as a composite material, typically a fibre-reinforced polymer.
The invention especially relates to a gas turbine engine component comprising a plurality of circumferentially spaced load carrying vanes extending in a radial direction of the ring element, wherein the load carrying vanes have an internal structure with an anisotropic load carrying property, and wherein the internal structure is configured so that a main load carrying direction is in parallel with the extension direction of the load carrying vane.
The term “ring element”, as referred to herein, may comprise only a part, i.e. a sector, of a ring, or a continuous full ring. Further, the ring element may form part of a housing, casing, or other similar component.
Turbojet engines may comprise a fan part that comprises a channel defined by an outer ring element, or outer casing, and an inner ring element, or inner casing. There is also a plurality of guide vanes and structural vanes extending in a radial direction between the outer ring element and the inner ring element. There is also provided an engine mount by means of which the engine is to be suspended in a frame, preferably a wing, of an aircraft. Thereby, the engine mount may be attached to the above-mentioned outer ring element. For the purpose of saving weight some of the above-mentioned components, such as the guide vanes and the outer ring element may be made of a composite material such as a fibre-reinforced polymer.
Typically, a structure like the one mentioned above will be subjected to large mechanical forces in many directions upon operation of the engine. When a material such as a fibre-reinforced polymer is used for some of said components these components will present a high ability of absorbing forces, i.e. a high tensile strength, in the lengthwise direction of the fibres. Typically, the fibres are oriented in a plane. More specifically, there may be four fibre directions in the plane. However, when and where a bending force is to be absorbed by such a component in a joint to another element, the ability of absorbing said force will be heavily reduced due to the incapacity of said material when it comes to the absorption of forces in a direction cross-wise to the fibre plane. Specifically, a joint between a vane with said arrangement of the fibres in a fibre plane and the outer ring element would have a low ability of absorbing a force in a direction cross-wise to the fibre plane. In other words, the bending rigidity of such a material is relatively low. In this respect the material presents a rather remarkable anisotropy.
U.S. Pat. No. 5,320,490 discloses a casing structural arm of a gas turbine engine component, wherein said arm is connected to an outer ring element and an internal inner ring element. The arm, which may be made of a composite material, presents four corners, two of which meet the outer ring element and the other two of which meet the inner ring element. In each corner there is provided a brace, made of metal, which is used for the fixing of the arm in relation to the outer ring element and the inner ring element respectively. The braces make it possible to link the arms directly with the inner ring element and the metallic outer ring element while ensuring the proper transmission of stresses through these arms.
U.S. Pat. No. 5,740,674 discloses an arrangement of aerodynamic and structural vanes of a gas turbine engine component, said vanes extending in a radial direction of the engine and being fixed between an outer ring element and an inner ring element of the casing. The groups of aerodynamic vanes are solidly attached to respective flanges which are screwed onto the outer ring element. Pairs of aerodynamic vanes are connected by one and same, common flange.
It is desirable to present a gas turbine engine component, which is of relatively light weight and provides a sufficient mechanical strength, and which promotes the use of light weight materials, such as composites of fibre-reinforced polymers, that might be of anisotropic character for the design of the vanes and/or a ring element of the engine.
According to an aspect of the present invention, a gas turbine engine component is provided comprising at least one ring element, and a plurality of circumferentially spaced load carrying vanes extending in a radial direction of the ring element, wherein the load carrying vanes have an internal structure with an anisotropic load carrying property, and wherein the internal structure is configured so that a main load carrying direction is in parallel with the extension direction of the load carrying vane, characterized in that the component comprises a stiffening structure bridging the distance between at least two adjacent load carrying vanes in the circumferential direction of the ring element, and that said at least two adjacent load carrying vanes are attached to the stiffening structure.
Preferably, the load carrying vane comprises a composite material. Especially, the composite material comprises a plurality of fibres oriented in a plane, which is in parallel to the extension direction of the load carrying vane and an axial direction of the component. Especially, the fibres extend in at least two directions in said plane, wherein a first direction is in parallel with the extension direction of the load carrying vane and a second direction is in parallel with the axial direction of the component. Thus, the first fibre direction defines the main load carrying direction and the second fibre direction defines a secondary load carrying direction. The first and second fibre directions are preferably perpendicular relative to one another.
The invention creates conditions for a joint between the load carrying vane and the stiffening structure, which is of high strength and high stiffness. More specifically, the joint is adapted so that the forces during operation will be directed in a fibre plane of the composite material of the load carrying vane, wherein the joint will have high strength. Further the joint is adapted to secure the load carrying vane in way that the joint will have a high stiffness.
Further, the invention creates conditions for using a light weight outer ring element, that still will be able to adopt the forces in an axial direction that it will be subjected to during engine operation. Preferably, the ring element comprises a composite material. In other words, the primary loads (radial to circumferential direction) are carried by the joint between the load carrying vane and the stiffening structure, wherein the ring element is substantially free from the primary loads.
Further, the stiffening structure is configured for distributing and/or transferring loads, especially radial to circumferential loads. Especially, the stiffening structure may be configured for transferring loads between the load carrying vanes and an engine mount. The ring element may be configured for connection of the component to adjacent gas turbine components in an axial direction of the gas turbine. The ring element may further be configured for transferring axial loads and/or sealing an interior space. The stiffening structure is preferably connected to the ring element in a way that no substantial loads in the radial direction are transferred between them. In other words, the stiffening structure is preferably connected to the ring element in a way that solely fixes their mutual positions. The stiffening structure is preferably positioned on a radial interior side of the ring element.
According to one embodiment, the stiffening structure is adapted for a higher bending strength than the load carrying vane. By supplementing the load carrying vane with a material of higher bending strength in a transition region at its end(s), the component will get an improved ability to withstand bending forces upon operation of said engine. Preferably, the stiffening structure is formed by a metallic material. According to a preferred embodiment, the stiffening structure comprises a plurality of sets of attachment portions, that the sets are spaced in the extension direction of the stiffening structure such that they match the distance between the load carrying vanes. Further, the gas turbine engine component comprises a plurality of attachment members and that each attachment member is adapted to connect one of said load carrying vanes to the attachment portions of the stiffening structure. The attachment member is adapted to achieve a high stiffness joint between the load carrying vane and the stiffness structure. In this way, the stiffening structure may be formed by a continuous ring and each load carrying vane may be bolted between an attachment member and a web of the stiffening structure.
According to an aspect of the present invention, a gas turbine engine component is provided comprising an outer ring element, a plurality of circumferentially spaced load carrying vanes extending in a radial direction of the ring element, and a load transferring element adapted to transfer loads to and/or from the load carrying vanes characterized in that the component comprises a stiffening structure bridging the distance between at least two adjacent load carrying vanes in the circumferential direction of the ring element, and that said at least two adjacent load carrying vanes are attached to the stiffening structure, that the stiffening structure is positioned on a radial interior side of the ring element and that the load transferring element is directly connected to the stiffening structure. The load transferring element may constitute an engine mount.
By the provision of the stiffening structure, the outer ring element does not need to be configured to carry any substantial radial loads between the load carrying vanes and the load transferring element. Thus, the invention creates conditions for using a light weight outer ring element, that still will be able to adopt the forces in an axial direction that it will be subjected to during engine operation. Preferably, the outer ring element comprises a composite material.
According to an aspect of the present invention, a gas turbine engine component is provided comprising at least one ring element, a plurality of circumferentially spaced arms extending in a radial direction of the ring element, and at least one attachment means adapted to attach at least one of said arms to said ring element, characterized in that the attachment means comprises a material that presents different properties in relation to the arm and/or the ring element, and that the attachment means form a stiffening structure bridging the distance between at least two adjacent arms in the circumferential direction of the ring element.
Preferably, the at least one attachment means is a separate part which is attachable to and removable from the arms to which it is connected. Preferably, it is also attachable to and removable from the ring element. According to one embodiment, the attachment means forms a bracket.
According to one embodiment, the arm and/or the ring element has an internal structure with an anisotropic load carrying property, and that the internal structure is configured so that a main load carrying direction is in parallel with the extension direction of the arm or the ring element, respectively. Preferably, a composite material is used comprising a plurality of fibres oriented in a plane, which is in parallel to a longitudinal direction of the arm and an axial direction of the component. Especially, the fibres extending in a at least two directions in said plane, wherein a first direction is in parallel with the longitudinal direction of the arm and a second direction is in parallel with the axial direction of the component.
Aerodynamic or structural arms or vanes of a light weight material presents a relatively low bending strength, and for that reason is facilitated by a supplement of a material of higher bending strength in a transition region in which it is connected to an outer ring element in order to withstand bending forces upon operation of said engine. Further, the invention creates conditions for a light weight outer ring element, that still will be able to adopt the forces in a circumferential direction that it will be subjected to during engine operation.
According to one embodiment, the attachment means therefore comprises a material of a higher bending strength than the material of the arm and/or the ring element. According to an alternative or complement, a geometry of the attachment means is designed for achieving an enhanced bending strength. Further, a metallic material is especially useful for this purpose since it can easily be formed to a suitable shape with preserved strength.
According to one embodiment, the attachment means comprises a material of a substantially isotropic internal structure.
According to one embodiment, the attachment means comprises a metallic material. Preferably, the metal is of a light weight, high strength and stiffness material such as an aluminum alloy or a titanium alloy.
According to an aspect of the present invention, a gas turbine engine component is provided comprising at least one ring element, a plurality of circumferentially spaced arms extending in a radial direction of the ring element, and at least one attachment means adapted to attach at least one of said arms to said ring element, characterized in that the arm and/or the ring element has a main load carrying direction in parallel with its extension direction and that said attachment means forms a stiffening structure bridging the distance between at least two adjacent arms in the circumferential direction of the ring element.
According to one embodiment, the arm is attached to both an outer ring element.
Accordingly, the ring element according to the invention may be either an outer ring or an inner ring to which the arms are attached. Further, said attachment means may be provided only for attaching the arm at one end to the outer ring element, or at both ends. Thus, different types of attachment means may be used for the inner ring and the outer ring.
According to one embodiment, said stiffening structure extends along an arc of a circle sector of at least 45°, preferably at least 90°, or most preferably at least 180°. According to one embodiment, the circumferential length along which said stiffening structure extends at least over a distance corresponding to a part of the component which is assumed to adopt a major part of the forces between an engine and an engine mount arranged for the purpose of holding or suspending the engine in relation to an aircraft. Said engine mount may be designed so as to be in engagement with the stiffening structure along a part of the arc of a circle sector defined by said casing or outer ring element. Said stiffening structure formed by said at least one attachment means should, preferably, extend along at least said part engaged with the engine mount, or even beyond that part in the circumferential direction. The engine mount may be connected directly the stiffening structure. Said stiffening structure will promote the use of a light weight material of the ring element to which it is connected, since it will supplement the load-carrying capacity thereof.
According to one embodiment, said stiffening structure extends continuously along the whole length of the arc of a circle. Thereby, said structure defines an annular element, contributing fully to the strength of the ring element to which it is connected. Accordingly, the use of a light weight, possibly anisotropic material as the ring element is promoted, since a substantial addition to the load-carrying capacity thereof is provided for by said structure formed by the arms and attachment means.
According to one embodiment, said ring element is an outer ring element, and said at least one attachment means is attached to and connects said plurality of arms to said ring element, wherein said gas turbine component comprises an engine mount provided on the outside of the outer ring element, the engine mount being attached to said at least one attachment means.
According to one embodiment, the outer ring element presents at least one radial opening through which the engine mount extends.
According to one embodiment, the gas turbine component comprises a plurality of said attachment means, each of which extends between and is attached to one of two adjacent arms of said plurality of arms.
According to one embodiment, the gas turbine component comprises a plurality of said attachment means, each of which extends between and is attached to two adjacent arms of said plurality of arms.
According to one embodiment, the at least one attachment means is attached by means of bolts to said ring element.
According to one embodiment, the at least one attachment means is attached by means bolts to said plurality of arms.
According to one embodiment, the plurality of arms constitute vanes of a fan of a turbojet engine.
According to one embodiment, said plurality of arms comprises force-absorbing structural vanes (load carrying vanes). According to a further development of the last-mentioned embodiment, at least one of the plurality of load carrying vanes attached to the stiffening structure has an aerodynamic shape and thereby forms an aerodynamic guide vane.
One advantage with the abovementioned component design with an attachment means (bracket) that is a separate piece and is possible to disassemble from the arm is that such a configuration creates conditions for disassembly for maintenance and repair.
Further features and advantages of the present invention will be presented in the following detailed description of a preferred embodiment.